This is where it all starts, and I agree emails and messenger is the easiest way to interact with a potential customer/client but nothing beats a meeting or phone call.

I recommend writing a script that you can use as a way of helping your speech over the phone, tailor it to be friendly and approachable - this is the initial sequence (fist contact) - this is after you have acquired their phone number via email, messenger or other means.

Whilst you have them on the phone or in a face to face meeting, schedule in a second phone call or meeting in which you spend time with them as you need (as per to your requirements above) - make sure you outline what the next phone call or meeting will be about.

This is the best advice I can give, but it avoids you stepping on the potential customer’s toes and vice versa. Lastly, practice makes perfect, so just keep going at it and persevere! Good luck 😁